Nontrivial Ground State Degeneracy of the Spin-Pseudospin Model of a Two-Dimensional Magnet Near the Frustration Point

TL;DR

This study uses classical Monte Carlo simulations to analyze the ground state degeneracy and phase transitions in a two-dimensional spin-pseudospin model with competing interactions, revealing first-order transitions near the frustration point.

Contribution

It demonstrates the presence of ground state degeneracy and first-order phase transitions in a 2D spin-pseudospin model near the frustration point, using histogram analysis of Monte Carlo data.

Findings

Ground state degeneracy occurs in the frustration area.

First-order phase transitions are observed near the frustration point.

Degeneracy involves two different ordered states.

Abstract

The classical Monte Carlo method is used to study the properties of the ground state and phase transitions of the spin-pseudospin model, which describes a two-dimensional Ising magnet with competing charge and spin interactions. This competition leads to the ground state degeneracy and the frustration of the system. It is shown that the ground state degeneracy is observed in the frustration area with nonzero probabilities of the formation of two different ordered states. Based on the histogram analysis of the Monte Carlo data, the type of phase transitions is analyzed. It is found that, near the frustration point, first-order phase transitions are observed in the dependence on the ratio between the spin ($s = 1/2$) and pseudospin ($S = 1$) interactions.